I 2R a Puma (no frame) and for overnight runs replace the rear thwart with a Yeti cooler, that I selected specifically to fit tight between the tubes. I strap it to the laces with 4 cam straps, just like the thwarts are installed. I line up the camstraps so the buckle doesn't get pinched and I can easily undo all 4 and pull the cooler out and take it to camp so I don't have to walk for food/beer.
I makes the raft more stable - I can set my beer on it for moderate rapids and it'll be fine, hell I could draft on it in moderate rapids, and I don't see any sign of or suspect any undue wear - the Yeti is very smooth plastic against the PVC.
I must admit I'm an unconventional newb so my my advice should be taken with a grain of salt, but I've loved how this configuration has worked out in the ~20 days I've used it thus far.